Freshwater ecosystems are strongly influenced by weather extremes such as heatwaves (HWs), which are predicted to increase in frequency and magnitude in the future. In addition to these climate extremes, the freshwater realm is impacted by the exposure to various classes of chemicals emitted by anthropogenic activities. Currently, there is limited knowledge on how the combined exposure to HWs and chemicals affects the structure and functioning of freshwater ecosystems. Here, we review the available literature describing the single and combined effects of HWs and chemicals on different levels of biological organization, to obtain a holistic view of their potential interactive effects. We only found a few studies (13 out of the 61 studies included in this review) that investigated the biological effects of HWs in combination with chemical pollution. The reported interactive effects of HWs and chemicals varied largely not only within the different trophic levels but also depending on the studied endpoints for populations or individuals. Hence, owing also to the little number of studies available, no consistent interactive effects could be highlighted at any level of biological organization. Moreover, we found an imbalance towards single species and population experiments, with only five studies using a multitrophic approach. This results in a knowledge gap for relevant community and ecosystem level endpoints, which prevents the exploration of important indirect effects that can compromise food web stability. Moreover, this knowledge gap impairs the validity of chemical risk assessments and our ability to protect ecosystems. Finally, we highlight the urgency of integrating extreme events into multiple stressors studies and provide specific recommendations to guide further experimental research in this regard.

中文翻译：

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热浪和微污染物对淡水生态系统的综合影响：综合评估多种压力源研究中的极端事件

淡水生态系统受到极端天气如热浪 (HW) 的强烈影响，预计未来热浪的频率和幅度会增加。除了这些极端气候之外，淡水领域还受到人类活动排放的各类化学物质的影响。目前，关于 HWs 和化学品的联合暴露如何影响淡水生态系统的结构和功能的知识有限。在这里，我们回顾了描述 HW 和化学品对不同生物组织水平的单一和组合影响的现有文献，以全面了解它们潜在的相互作用效应。我们只发现了几项研究（本综述纳入的 61 项研究中的 13 项）调查了 HW 与化学污染相结合的生物效应。报告的 HWs 和化学物质的交互作用不仅在不同的营养水平内变化很大，而且还取决于人群或个人的研究终点。因此，由于可用的研究数量很少，在生物组织的任何层面都不能突出一致的交互作用。此外，我们发现单一物种和种群实验的不平衡，只有五项研究使用多营养方法。这导致相关社区和生态系统水平端点的知识差距，从而阻止探索可能损害食物网稳定性的重要间接影响。此外，这种知识差距削弱了化学品风险评估的有效性和我们保护生态系统的能力。最后，